Receptacle filling apparatuses are known in which the substance to be packaged is metered by weighing. In particular, carrousels exist for filling receptacles in which a rotary chassis supports a feed hopper connected to a series of filler spouts via filler valves, each connected to an output of a weighing control unit having an input connected to scales carried by the rotary frame and disposed beneath a receptacle which is itself positioned immediately beneath a filling spout. The scales control opening or closing of a filling valve as a function of a weight measured relative to a reference value input to the scales. Metering by weighing has the advantage of keeping the measurement apparatus separate from the substance to be metered and it is not sensitive to temperature variation, or more generally to variation in the density of the substance.
However, for machines that are to operate at very high throughputs, as is now commonly required for reducing packaging costs, it is observed that under transient conditions, references to weight alone give rise to operating abnormalities related to said transient conditions. These abnormalities include, in particular: problems of foam forming when a receptacle begins to be filled; overflowing at the end of receptacle filling, particularly when an installation is switched on or off due to pressure variations in feed ducts resulting from a varying number of filling spouts being in operation; and disturbances resulting from variations in the viscosity of the substance due to variations in the temperature at which packaging takes place. In this context, it may be observed that when the viscosity of the substance varies a great deal with temperature, operation of the filling apparatus may be severely disturbed by variations in the temperature of the substance to be packaged. In this context, it may be observed that filling spouts are generally designed to operate on an on/off basis, so if the substance to be packaged is at a higher temperature than that for which the filling spouts are adjusted, and is therefore substantially more fluid, the substance to be packaged flows at a rate considerably higher than the design rate and this can result in considerable disturbance to the jet of substance which may lead to splashing or to variation to a greater or lesser extent in the dynamic pressure of the jet of substance on the free surface of substance already contained in the receptacle with considerable variation in the quantity of substance which continues to flow into the receptacle when the filling valve is closed, which variations must be compensated for by complex electronic systems.
An object of the invention is to provide apparatus for filling receptacles with metered weights and which compensates for at least some of the disturbances that result from transient conditions.